Fluoroquinolone resistance among clinical isolates of Streptococcus pneumoniae belonging to international multiresistant clones.

Twenty-nine fluoroquinolone (FQ)-resistant clinical isolates of Streptococcus pneumoniae from a collection of isolates from the Alexander Project (1992-1997) and a study from Northern Ireland were identified on the basis of ofloxacin MICs > or = 4 mg/L. DNA fingerprint analyses using BOX-fingerprinting and pulsed-field gel electrophoresis revealed serotype 9V and 23F high-level FQ-resistant strains indistinguishable from the pandemic Spain(23F)-1 and Spain(9V)-3 clones, the type strains of which are low-level resistant or susceptible to the fluoroquinolones.